The antigenic analysis of M. leprae will be investigated using polyclonal and monoclonal antibodies as immunological reagents. Emphasis will be placed on the production, characterization, and subsequent usage of the monoclonal antibodies to purify and characterize important immunogens of M. leprae. Antigens purified by affinity chromatography using monoclonal antibodies will be characterized as to their chemical nature, immunological relatedness with other mycobacteria and as to their immunogenicity in natural infections with M. leprae. Finally, monoclonal antibodies which are specific to M. leprae will be used to design a competitive binding immunoassay capable of detecting antibodies in human serum which are specific to M. leprae and thereby indicate an infection with M. leprae. The development and implementation of such a test may serve to raise the efficiency of diagnosis and subsequent treatment of leprosy and thus retard the spread of the disease world-wide.